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I met Tim through a
long-time buddy of mine, Kai. Tim is a jet turbine
engineer and used a CAD/simulation program to design a valveless
pulse jet engine. He described its operation during an
off-road trip last year, but I had never seen the engine in
operation. But a test run was being conducted in Borrego
Springs, so we loaded up Thor and headed to watch. The
engine has been mounted to an old motorcycle frame and
attached to a 30lb propane bottle in preparation for a test run.
We had trouble getting it started due to low fuel, but once a
new bottle was attached, it started right up. There is a link
to a youtube posting about 1/2 way down in this page.
The photos below are
what we saw.
examine the mechanical monstrosity called the rocket bike.
The engine has to be mounted well aft of the operator due to the
intense heat generated during operation. The whole setup
is "hillbilly deluxe", but it DOES work. The engineering
design that went into the engine was impressive, almost as
impressive as the effort put into the seat.
of the setup is confirmed by looking at the deluxe operator seat.
Thor is visible in the top right of the photo above.
previous run, the mounting bracket on the engine broke on rough
ground and the engine fell onto the rear fender and melted
the sheet metal!
fine heat shield on the fuel line. The line comes from the
tank, through the shield and then wraps around the engine to
allow the liquid propane to vaporize before being released into
the combustion chamber. The line goes from standard rubber
propane hose to copper tubing to aircraft grade stainless steel
tube for the entry into the engine. The whole assembly is
firmly attached to the high-quality frame using baling
wire. The high-tech aircraft-quality stainless steel and
TIG-welded engine provides a nice juxtaposition to the
scrap-heap construction of the support components! Nothing
says "quality" like baling wire, but there is a good reason for
this approach. During operation, the engine expands in length
due to the intense heat and the expansion would break any hard
mount points. So, the engine is only attached on the front
end via the bracket and then sits on a cradle on the rear.
The baling wire is only to keep the engine from bouncing out of
the cradle during bumps. Due to the length of the machine,
the engine has to be removed during transport to allow it to fit
on Kai's trailer.
propane tank is upside down to allow liquid propane to flow in
the pipe (as opposed to the normal vapor for a camp stove or
BBQ). The flow control is a needle valve attached to the
original motor mount. The whole setup is robustly secured
with a bungee cord which is not only colorful, but cost
regular spark plug is used to get the combustion started.
The wires must be removed after ignition because the intense
heat will melt the insulation and wires. The engine is
made from special high-temperature stainless steel because
regular steel will sag and melt.
resonance in the engine is initiated with a leaf blower or
getting dark, almost time for a run!
a certified observer, notes the position of the spark plug and
its similarity to certain anatomical features, only smaller (or
at least hopefully).
a frame-grab from video and since it was really dark it has
plenty of motion blur. But, you can see the heat generated
from the engine during operation. The noise is truly
daunting and it was good that I had my ear plugs with me.
the bike returns after a run and is preparing to shut down the
engine. Note the infrared illumination on the ground due
to the intense heat of the engine.
A video of the run is available on youtube here.
morning we got a chance to inspect some of the antique equipment
in Dan's yard.
There were ocotillos
blooming across the road.
of the San Filipe Valley on the way back to San Diego.
cactus in bloom near Banner, CA.
yucca blooms had an interesting odor; not good or bad, but
jet was impressive. The noise was daunting but the heat
glow after dark was awesome, something that has to be
experienced in person.
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